A: WiFi operates in the 2.4GHz and 5GHz license-exempt bands. License-exempt means that other technologies, including other wireless LANs (WLANs), cordless phones, and security systems, can deploy in this band.
However, more products are designed to work in the 2.4GHz band than in the 5GHz band. This is why people say that the 5GHz band is less crowded.
The 2.4GHz band is more popular because lower frequencies are generally more desirable. Signals propagate farther at lower frequencies, giving you better range. Also, the signal absorption is lower, giving you better coverage in cubed and walled offices.
In general, if you deploy in the 5GHz band, you lose coverage. As a result, you must deploy more access points (APs). However, the big advantage of deploying in the 5GHz band is that there is more spectrum available. This has two advantages:
- More channel choice—More channels mean that if a channel is noisy, you can deploy the AP to a different one. Today, high-end APs automatically detect and move to the cleanest channel, removing the need to monitor and configure the channel.
- Potential for high data rates—More channels mean a higher probability that you can deploy 40MHz channels versus 20MHz channels, which in turn enables you to transmit at twice the data rate.
Why do I say "probability"? Because IEEE 802.11n is defined such that if it senses noise in the band, it restricts itself to operating in a 20MHz band. Therefore, you get the benefit of higher data rates only when the band is relatively free of interference from other equipment.
So should you invest? I'd recommend that you do because the price of dual-mode APs is coming down. These APs are worth the money for the added bandwidth and flexibility that they give you.